Blast-actuated valve-closure system

ABSTRACT

A blast-actuated valve-closure system for closing an opening in response to the overpressure of a blast. The system comprises a plurality of louvers disposed across the opening in a normally open position. The louvers are fastened by cranks to a rod which is adapted to be moved by a rotatable actuating crank driven by a torsion spring. Normally, rotation of the actuating crank is blocked by two spring-loaded rollers interposed in a detent therein. A rotatable triggering crank is responsive to the impingement of a blast pressure wave on the louvers for unblocking the actuating crank which then effects movement of the rod for tilting the louvers to their closed position. A rotatable resetting crank is provided for restoring the actuating crank and the rod to their initial positions thereby moving the louvers to their open position. In addition, the actuating crank may alternatively be unblocked by electromechanical means which has its energization controlled either electrically by sensing devices or manually by an attendant.

United States Patent McCoy 51 May 16, 1972 [54] BLAST-ACTUATEDVALVE-CLOSURE SYSTEM [7 21 Inventor: Robert Gordon McCoy, Whippany, NJ.

Bell Telephone Laboratories, Incorporated, Murray Hill, BerkeleyHeights, NJ.

[22] Filed: May 26,1970

[21] Appl.No.: 40,527

[73] Assignee:

Primary Examiner-Edward J. Michael AltomeyR. J. Guenther and William L.Keefauver [57] ABSTRACT A blast-actuated valve-closure system forclosing an opening in response to the overpressure of a blast. Thesystem comprises a plurality of louvers disposed across the opening in anormally open position The louvers are fastened by cranks to a rod whichis adapted to be moved by a rotatable actuating crank driven by atorsion spring. Normally, rotation of the actuating crank is blocked bytwo spring-loaded rollers interposed in a detent therein. A rotatabletriggering crank is responsive to the impingement of a blast pressurewave on the louvers for unblocking the actuating crank which thenefi'ects movement of the rod for tilting the louvers to their closedposition. A rotatable resetting crank is provided for restoring theactuating crank and the rod to their initial positions thereby movingthe louvers to their open position. In addition, the actuating crank mayalternatively be unblocked by electromechanical means which has itsenergization controlled either electrically by sensing devices ormanually by an attendant.

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BACKGROUND OF THE INVENTION This invention relates to valve-closuresystems and, more particularly, to an improved valve-closure system thatis actuated automatically in response to the over-pressure of a blast.

Protection against blasts from atomic bombs or other severe explosionsmay be obtained by constructing a strongly reinforced chamber in afavorable location, such as at a suitable depth under the surface of theearth. A chamber of this type is usually equipped with a ventilatingsystem having a number of ducts extending from the chamber to thesurface of the ground. Some of these ducts function as intake ducts foradmitting fresh air to the chamber while other of the ducts serve asexhaust ducts for removing stale air from the chamber. Both of thesetypes of ducts are, in general, provided with valve-closure devices forsealing or closing them against overpressure when a blast occurs. Thisis especially necessary in the event of an atomic explosion in order toexclude radioactive fallout and destructively high blast pressures.

These valve-closure devices can be controlled by various types ofsensing systems which are designed to detect the occurrence of a blast.The sensing systems are usually designed to operate the valve-closingdevices so that they will be closed before the arrival of an airblastwave. In addition, as a safety precaution against a possible failure ofa sensing system, it is desirable that the valve-closing devices be sodesigned as to become closed automatically when a sudden overpressureimpinges upon them.

Heretofore, such automatically operated valve-closing devices have notbeen fully satisfactory because they have employed large closuremembers, usually a single closure member for a large valve. Because ofthe large unit blast pressures over large closure areas, the closuremembers and, consequently, all associated moving parts, as well asbearings and fixed hardware, must be very massive to withstand the largestatic and dynamic loads resulting from airblast pressure loading,shock-front interaction, and heavy impact on seating. This heavyconstruction has been objectionable because it is expensive and itsoperation is not sufficiently rapid.

SUMMARY OF THE INVENTION The present invention is designed to overcomethe objections discussed above by providing an improved automaticallyoperated valve-closure system which is safer, faster, simpler, cheaper,and more reliable than valve closures of the prior art. Thevalve-closure system of this invention comprises a plurality of louverspivoted near their centers and mounted across the opening of aventilating duct in a normally open position. The louvers areindividually fastened by connecting cranks to a common operating rodwhich is adapted to be moved by a rotatable actuating crank driven by atorsion spring. Normally, the rotation of the actuating crank is blockedby locking means comprising two rollers interposed in a detent formedtherein.

A rotatable triggering crank is responsive to the impingement of a blastpressure wave on the louvers for efiecting the unblocking of theactuating crank through the removal of the rollers from their interposedpositions. Upon being thus unblocked, the actuating crank is rotated bythe torsion spring and drives or pulls the operating rod to a positionwhere the associated connecting cranks effect the tilting of the louversto their closed position thereby closing the opening in the ventilatingduct.

A rotatable resetting crank is provided for utilizing the rollers andthe detent to restore the actuating crank and the operating rod to theirinitial positions thereby effecting the return of the louvers to theirnormally open position.

The unblocking function of the rotatable triggering crank mayalternatively be performed by electromechanical triggering means havingits energization controlled either manually by an attendant orelectrically by a suitable blast-sensing device.

BRIEF DESCRIPTION OF THE DRAWING The features of this invention are morefully discussed hereinafter in relation to the following detaileddescription of the drawing in which:

FIG. 1 is a front view of an exemplary embodiment of the valve-closuresystem of this invention;

FIG. 2 is a perspective view of the valve-closure system mounted acrossthe opening of a duct that is located in a concrete emplacement;

FIG. 3 is an exploded perspective view of the chief operating componentsof the valve-closure system;

FIG. 4 is a side view, partly in section, of a portion of thevalve-closure system with the louver blades in their normally openposition and some of the components of the valveoperating equipment intheir normally unoperated or idle positions;

FIG. 5 is a side view that is somewhat similar to FIG. 4 but showing thelouver blades in their closed position with some of the other componentsof the valve-operating equipment in their operated or active positions;

FIG. 6 is a side view that is somewhat similar to FIG. 5 but which showsthe resetting crank, which is employed in the valve-operating equipment,in its operated or active position;

FIG. 7 is an end view, partly in section, of the locking mechanism andthe triggering mechanisms which are used in the valve-operatingequipment;

FIG. 8 is a partly sectionalized side view that is somewhat similar toFIG. 4 but which illustrates a number of additional components of thevalve-operating equipment;

FIG. 9 is a partly sectionalized side view taken from the oppositedirection of that used for FIG. 8 and showing additional components ofthe valve-operating equipment;

FIG. 10 is a schematic diagram of exemplary circuits utilized forcontrolling the operation of the motor employed in the valve-operatingequipment; 7

FIG. 11 is a schematic diagram of exemplary circuits used forcontrolling the energization of the solenoid that is incorporated in thevalve-closing equipment;

FIG. 12 is a partly sectionalized side view, taken along the line 12-12in FIG. 7, of the locking mechanism;

FIG. 13 is a detailed side view, partly in section, of normallyunoperated resetting means which is adapted for resetting the lockingmechanism after it has been released;

FIG. 14 is a detailed side view that is somewhat similar to FIG. 13 butwhich shows the resetting means in a partly operated condition;

FIG. 15 is a detailed side view that is somewhat similar to FIG. 14 butwhich shows the resetting means in a fully operated condition; and

FIG. 16 is a detailed side view, partly in section, of a portion of theoperating rod and some of the components of the valveoperating systemthat are associated with it.

DETAILED DESCRIPTION An exemplary blast-actuated valve-closure system inaccordance with this invention is broadly illustrated in FIG. 1 and FIG.2. It can be seen in FIG. 2 that the valve-closure system is associatedwith a ventilating duct 1 extending to an underground chamber which isnot shown as it forms no part of the invention. The duct 1 may be eitheran intake duct or an exhaust duct and is securely held by a concreteemplacement or support 2. The mouth or opening of the duct 1 may haveany convenient shape, such as that of arectangle. A louver valve-closuredevice 3 is securely mounted in abutting relationship across the openingof the duct 1 as is represented by FIG. 2.

The louver valve-closure device 3 is provided with a heavy rectangularframe 4 having a number of strong cross-ribs 5. The ribs 5 are spacedequidistantly apart and are immovably fastened to the frame 4. Each ofthe ribs 5 has a louver blade 6 pivotally attached thereto by suitablecontinuous hinge means 7. Each of the hinge means 7 is disposed near thecenter of the cross-section of its associated louver blade 6 as is bestseen in FIG. 3 and FIG. 8. The louver blades 6 are parallelly disposedand, when closed, form covering means for the opening of the duct 1.Each of the blades 6 has a tapered chevron-shaped cross-section, as isbest seen in FIG. 8,.and is designed to rotate through a stroke of about70.

One of the blades 6 is shown in the upper portion of FIG. 8 and itshould be noted that the distance between its right edge and the hinge 7is slightly less than the distance between its left edge and the hinge7. This hinge eccentricity is provided for the purpose of assisting indeveloping aerodynamic torque and to insure that blast pressureimpinging on the valve 3, after it has been closed, cannot reopen it.

A plurality of connecting cranks 8 are associated with the louver blades6. Each of the cranks 8 has one end fixedly and immovably attached to arespectively different one of the blades 6 at a point in the middle ofthe length thereof. The other end of each of the cranks 8 is pivotallyattached by appropriate hinge means 9, as is best indicated in FIG. 3,to a hollow operating rod 10 which is adapted to be moved up and downalong its longitudinal axis by means described hereinafter.

A portion of one side of the rod 10 is cut away so that the ends of thecranks 8 can enter the cavity formed by the hollow interior of the rod10 and thus receive the hinge means 9. Theoretically, the operating rod10 may be constituted by a unitary member. However, as a practicalexpedient, it is shown in the drawing as being a composite rod which isformed in sections that are joined together by conventional couplingmeans.

When the operating rod 10 is moved to the limit of its extent of travelin one direction, the connecting cranks 8 effect the rotation of thelouver blades 6 to their open position where, as is shown in FIG. 2 andalso in FIG. 4, they uncover the opening of the duct 1. Then, when theoperating rod 10 is moved to the limit of its extent of travel in theopposite direction, the pivotally-mounted connecting cranks 8 will pullthe louver blades 6 into their closed position where, as is shown inFIG. 1 and also in FIG. 5, the blades 6 overlap in flat array therebycovering, or closing, the opening of the duct 1.

It should be noted that the tapered chevron shape of the cross-sectionof each of the louver blades 6 minimizes air flow losses and assists, incombination with the above described location of the hinge means 7, toproduce aerodynamic closing torques.

The construction and configuration of the valve-closure device 3 isespecially suited for fast closing action because of its low inertia.This is because the valve-closure device 3, instead of being a large,single device, comprises a number of low-inertia blades 6. For equalclosing times, the ratio of the actuating force required for this valveto that required for most of the prior art valves is less than 0.01.This ganged array of balanced blades 6 has the additional advantages ofminimizing the energy which must be absorbed when it is rapidly closed,and of spreading the minimized impact energy fairly evenly over thelarge elastic field of the blades 6.

The louver blades 6 are normally in an open position because theoperating rod 10 is normally in its unoperated position shown in FIG. 3and also in FIG. 4. When it is desired to tilt the louver blades 6 totheir closed position, the operating rod 10 must be moved to itsoperated position shown in FIG. 5. This movement of the operating rod 10is effected by an actuator crank 11.

THE ACTUATOR CRANK As is shown in FIG. 3, one end of the actuator crank11 is bifurcated or divided into two branches. The ends of thesebranches are pierced for receiving therein an instrumentality,constituted by a coupling pin 12, which extends through the walls of thehollow operating rod 10. A blade 13, having a shouldered end, isvertically disposed inside the cavity formed by the hollow interior ofthe rod 10. As is shown in FIG. 16, the blade 13 has its shouldered endin engagement with that portion of the coupling pin 12 which extendsbetween the branches of the bifurcated end of the actuator crank 11. Thefunction performed by this blade 13 is explained hereinafter.

The actuator crank 11 is normally in its idle position, shown in FIG. 3and also in FIG. 4, wherein it holds the operating rod 10 in itsunoperated position. This causes the operating rod 10 to hold thecovering means, comprising the louver blades 6, in its open position.The actuator crank 11 is rotatably mounted on a pivot rod 14 and isadapted to be rotated to its active position, shown in FIG. 5, inresponse to a driving force exerted by a coiled torsion spring 15 whichis best seen in FIG. 3. This torsion spring 15 has one end fixedlyconnected by any suitable means, such as a clamp, to an anchor plate 16which, as is indicated by broken lines in FIG. 3, is fastened to aportion of the valve-operating equipment frame 35 by any convenientmeans, such as bolts. The other end of the torsion spring 15 is fixedlyattached to a driving thimble 30 by appropriate clamping means 300 and30d. The driving thimble 30 is rotatably mounted on the pivot rod 14, asis indicated by a broken line in FIG. 3. The bottom part of the drivingthimble '30 has a protruding portion with a squared end 301': which isadapted to be received within a hole 30b in the actuator crank 11 and issecurely retained therein by axial confinement for the purpose ofapplying a driving torque to the actuator crank l 1.

In this exemplary embodiment of the invention, the torsion spring 15 isnormally wound so as to be torsionally stressed. It is designed to exerta starting torque of approximately 900 inch-pounds which can be used forrotating the actuator crank 11 so that its bifurcated end will movedownward to its active position, shown in FIG. 5, thereby moving theoperating rod 10 downward to its operated position. This movement of theoperating rod 10 will cause the covering means, comprising the louverblades 6, to move to its closed position wherein the opening of the duct1 will be closed.

THE LOCKING MEANS However, the driving force of the torsion spring 15and the rotation of the actuator crank 11 are normally blocked bylocking means. The locking means have a first position for normallyholding, or locking, the actuator crank 11 in its idle position. Inaddition, the locking means have a second position adapted forunblocking or releasing the actuator crank 11. The locking meanscomprise two locking, or trip, rollers 17 normally interposed one abovethe other in a composite detent.

Specifically, this composite detent comprises a hole or cavity 18 formedin the actuator crank 11. The cavity 18 contains two spaced pins ordouble fingers 19 which are attached to the actuator crank 11 by meansdescribed hereinafter and which are so disposed as to support the lowerone of the rollers 17 as is shown in FIG. 7. The detent furthercomprises a third pin or holding finger 21 attached to a resetting crank22. This resetting crank 22,which is normally stationary, is rotatablymounted on the pivot rod 14 in a position adjacent to one side of theactuator crank 11 for a purpose that is explained hereinafter.

The third finger 21 is adapted to protrude from the resetting crank 22in such a manner as to bear on the upper one of the trip rollers 17 asis shown in FIG. 7. Thus, the holding finger 21 and the locking rollers17 function to prevent the double fingers 19 and their associatedportion of the actuator crank 11 from moving upward. It should be notedthat the position of the holding finger 21 is above a space 23 which, asis shown in FIG. 12, is formed between the two pin or finger elements ofthe double fingers 19. This space 23 is made atleast equal to the widthof the holding finger 21 and is sufficiently large to allow the holdingfinger 21 to pass therethrough when the locking rollers 17 are removedfrom their interposed position and the double fingers 19 are movedupward by the actuator crank 11 in the manner described hereinafter.

THE TRIGGER MEANS Trigger means are provided for moving the lockingrollers 17 from their interposed position to their second position foreffecting the release of the actuator crank 11 from its idle position.The trigger means comprise a trigger spring 24 coiled around a triggerplunger 20. As is best seen in FIG. 7, both the spring 24 and theplunger 20 are disposed in a cavity 25 formed in a block 26 which issecurely fastened to one side of the actuator crank 1 1. One end of theplunger 20 extends through a hole in the block 26 for a purpose that isdescribed hereinafter. One end of the trigger spring 24 rests against aportion of the block 26 and its other end bears against the enlargedhead of the plunger 20 for pressing it against one side of the rollers17. Normally, the trigger spring 24 is compressed so that it exertspressure against the rollers 17.

The force exerted by the spring 24 and the plunger 20 against one sideof the rollers 17 is normally ineffective to move them because the otherside of the rollers 17 abuts against a disk 27 which is fastened to oneend of a plunger 28 in a solenoid 29. The solenoid 29 is normallyenergized and, consequently, pushes its plunger 28 and the disk 27toward the left in FIG. 7 with sufficient force for holding the rollers17 firmly against the head of the trigger plunger 20 thereby overcomingthe force exerted by the trigger spring 24. The vertical alignment ofthe rollers 17 is maintained by the fact that the disk 27 also causesthe ends of the rollers to press against the interior face of the block26.

It should be noted that a portion of the resetting crank 22 is recessedfor forming a cavity 31 in the area around the disk 27. This cavity 31is of sufficient size to receive therein the rollers 17 but they arenormally prevented from entering it by the presence of the disk 27 whichis held therein at this time by the force exerted by the solenoid 29.

CLOSING THE LOUVER BLADES When it is desired to move the louver blades 6to their closed position for closing the opening of the duct 1, therestraining or blocking force presented by the solenoid 29 must beovercome. This can be accomplished by several different methods whichare explained hereinafter. In response to using any one ofthese methods,the plunger 28 and the disk 27 are forced to move toward the right inFIG. 7 thereby vacating the left portion of the cavity 31, This permitsthe trigger spring 24 and the trigger plunger 20 to push the lockingrollers 17 into the cavity 31 thereby unblocking or releasing the doublefingers 19. Accordingly, the double fingers l9 and their associatedportion of the actuator crank 11 are now free to be rotated or movedupward in response to the driving force exerted by the torsion springwhich is normally wound so as to be torsionally stressed.

It should be noted that this portion of the actuator crank 11 has anarcuate groove or trough 32 formed therein as is best seen in FIG. 12.This groove 32 is of sufficient size to accommodate or to receivetherein the end portion of the holding finger 21. The reason for this isthat the holding finger 21 is attached to the resetting crank 22 whichremains stationary during the upward rotation of this portion of theactuator crank 11. Accordingly, when this portion of the actuator crank11 is rotated upward, the groove 32 and the space 23 between the doublefingers 19 travel past the protruding portion of the holding finger 21and thus enable the actuator crank 11 to rotate freely without, at thistime, being blocked by the holding finger 21.

When the double fingers l9 and their associated portion of the actuatorcrank 11 rotate upward, the other, or bifurcated, portion of theactuator crank 11 rotates downward to its active position, as isrepresented in FIG. 5. As was stated above, since this end of theactuator crank 11 is joined by the coupling pin 12 to the operating rod10, this rotation of the actuator crank 1 1 causes the operating rod 10to be pulled down to its operated position thereby tilting the louverblades 6 to their closed position, as is shown in FIG. 5, and thusclosing the opening of the duct 1.

The resulting abutment of the edges of the louver blades 6 against eachother restrains the operating rod 10 from further downward movement andthis, in turn, prevents further rotation of the actuator crank 11.

It should be noted that the operation of the actuator crank 11 and theoperation of the torsion spring 15 are entirely rotary; This rotaryoperation produces the following advantages: it minimizes inertia of theparts, simplifies the constructional details, minimizes the number andcomplexity of the bearings, and also minimizes the effects of friction.

STARTING THE UPWARD ROTATION OF THE RESETTING CRANK At a point in timenear the end of the abovementioned rotation of the actuator crank 11, acam 33, which is attached to one side of the actuator crank 11, movesinto engagement, as is represented in FIG. 5, with a normally opencontrol switch 34 which is fastened to the frame 35 of the valve-closureequipment. The engagement of the cam 33 with the control switch 34closes the switch 34 and thereby closes an obvious circuit, shown inFIG. 10, for energizing a relay 53.

In response to being energized, the relay 53 operates its armature andthereby efiects the closure of a forward power supply circuit 36 forapplying electric energy from a suitable source 37 of electric power foroperating a conventional reversible electric gear motor 38 in a forwarddirection. This gear motor 38 has a shaft 39 on which a pinion gear 41is mounted in meshing engagement with gear teeth 42 formed in an edge ofthe resetting crank 22. Accordingly, the motor 38 is now energized in aforward direction so as to cause its pinion gear 41 to drive the gearteeth 42 in a direction such that the resetting crank 22 will be rotatedupward in the same direction as that in which the actuator crank 11 wasrotated when it effected the closure of the louver blades 6.

THE TRIGGER RESETTING MECHANISM Attention should now be directed to thetrigger resetting mechanism which is associated with the solenoid 29. Asis shown in FIG. 7, the solenoid 29 is enclosed within a container 43which is securely fastened by means of screws driven into a plurality ofstuds 44 formed on one side of the resetting crank 22. Thus, when theresetting crank 22 isrotated, it carries the container 43 and thesolenoid 29 with it. The trigger resetting mechanism is positionedwithin the container 43 and is located adjacent to the right end of thesolenoid 29.

The trigger resetting mechanism, as is shown in FIG. 13, includes acollapsible spring-loaded linking-mechanism comprising a compressedspring 45 disposed between a left washer 46 and a right washer 47 whichare adapted to slide back and forth within the container 43. The leftwasher 46 has an axially extending bushing on each of its sides. Theright bushing on the left washer 46 is designed to function as a slidingbearing for assisting in stabilizing the left washer 46 by preventing itfrom tilting. The left bushing on the left washer 46 has a central borefor receiving therein the head of a retaining shouldered screw 48 whichnormally abuts against the left washer 46.

The screw 48 extends through the spring 45 and also through a hole inthe right washer 47. The point of the screw 48 is driven into the baseof a control button 49 which abuts against the right washer 47 Thiscontrol button 49 is slidably positioned in a hole in the end of thecontainer 43. Due to the pressure exerted by the spring 45 against theright washer 47, the conically-shaped external end of the control button49 normally protrudes outside the container 43 to the extent Shown inFIG. 13.

When the resetting crank 22 approaches the limit of its rotation,control means must be utilized to effect its stopping at the properpoint. These control means include a cam 51 which, as is shown in FIG.9, is mounted on the resetting crank 22 near the toothed edge thereof.The control means also include a normally closed limit switch 52 whichis mounted on a bracket 40 that is attached to the frame of thevalve-closure equipment.

While the toothed edge of the resetting crank 22 is rotating upward, itmoves the cam 51 upward to its position shown in dotted lines in FIG. 9.This upward position of the cam 51 causes the cam 51 to engage and openthe normally closed limit switch 52. As can be understood frominspection of FIG. 10, the opening of the switch 52 effects thedeenergization of the relay 53 which consequently releases its armatureand thereby effects the opening of the power supply circuit 36 of themotor 38. This stops the motor 38 and thus terminates the upwardrotation of the resetting crank 22.

PINNING THE ACTUATOR CRANK TO THE RESETTING CRANK Slightly before themotor 38 is stopped, the solenoid container 43, which is being carriedalong with the rotating resetting crank 22, is moved upward to itsposition shown in dotted lines in FIG. 9. This upward position of thesolenoid housing 43 causes the conical end of its control button 49 tocome into engagement with a stationary cam 54 that is fastened to theframe 35 of the valve-closure equipment.

The resulting engagement of the control button 49 with the cam 54 causesthe protruding portion of the control button 49 to be pushed toward thesolenoid 29 as is shown in FIG. 14. Normally, as is shown in FIG. 13,the control button 49, which can now be understood as constituting acam-operable instrumentality, abuts against the right washer 47 which isinside the solenoid container 43. In moving inward, the control button49 pushes the washer 47 toward the left, as is shown in FIG. 14, therebyfurther compressing the spring 45, as is also represented in FIG. 14.The inward motion of the control button 49 causes the head of the screw48 to move toward the left inside the left bushing on the left washer46.

The compressional force thus produced in the spring 45 tends to push theleft bushing on the left washer 46 toward the left in FIG. 14 so as toincrease its pressure against the plunger 28 of the solenoid 29. Thisincreased pressure tends to push the plunger 28 and its disk 27 towardthe left in FIG. 14 but such movement of the plunger 28 is blocked atthis time because the rollers 17 are held within the cavity 31 by thepresence of the adjacent side of the actuator crank 11. Accordingly,this pressure is maintained without producing any useful result untilthe rotation of the resetting crank 22 is nearly terminated.

Just before the rotation of the resetting crank 22 is terminated, therollers 17 in the cavity 31 will be carried into alignment with thecavity 18 in the actuator crank 11. Now,

' the pressure exerted by the spring 45, which is being transmitted bythe left washer 46 through the plunger 28 and the disk 27 to the rollers17, becomes effective to force the rollers 17 out of the cavity 31 inthe resetting crank 22 and into the cavity 18 in the actuator crank 1 1.This permits the plunger 28 and the disk 27 tomove to their positionsshown in FIG. 7. Also, the left washer 46 now moves to its positionshown in FIG. 15.

It should be noted that the trigger spring 24 and the plunger oppose theentry of the rollers 17 into the cavity 18. However, since the pressureexerted by the spring 45 is designed to be greater than that exerted bythe spring 24, the rollers 17 will enter the cavity 18 at this time andwill assume their previously described interposed position between thedouble fingers 19 on the actuator crank 11 and the holding finger 21 onthe resetting crank 22. This serves to pin the actuator crank 1 1 to theresetting crank 22. The trigger resetting action is now terminated withthe above-mentioned opening of the motor energizing circuit 36. Thevalve-closure system now remains in this closed and reset condition.

OPENING THE LOUVER BLADES When it is desired to open the louver blades6, a conventional manual control switch 55, which is normally open as isshown in FIG. 10, is manually operated for closing an obvious circuitfor energizing a relay 50. Upon being energized, relay 50 operates itsarmature to close a suitable reverse energizing circuit 56 forconnecting the power supply source 37 to the motor 38 in such a manneras to cause the motor 38 to operate in the reverse direction from thatpreviously described. Accordingly, the pinion gear 41 will now berotated in a direction opposite to that described above and willconsequently drive the gear teeth 42, which are on the edge of theresetting crank 22, in such a manner as to cause the resetting crank 22to rotate in a direction which is the opposite of its previouslydescribed rotation.

The reverse rotation of the resetting crank 22 will be accompanied bycorresponding reverse rotation of the actuator crank 11 due to the factthat they are pinned together by the double fingers 19, the rollers 17,and the holding finger 21 as was explained above. The reverse rotationof the actuator crank 11 carries the cam 33 out of engagement with theswitch 34 which thereupon reopens. Immediately thereafter, the reversemovement of the resetting crank 22 carries the cam 51 out of engagementwith the limit switch 52 which, consequently, becomes closed.

During the reverse rotation of the actuator crank 11, the torsion spring15, which has one end fixedly connected to the actuator crank 11 as wasdescribed above, will be wound so as to return to its original fullyenergized state or condition of being under full torsional stress. Also,at this time, the coupling pin 12, which couples the actuator crank 11to the operating rod 10, will force the operating rod 10 to move upward.This upward movement of the operating rod 10 will cause the connectingcranks 8, which couple the operating rod 10 to the louver blades 6, toforce the louver blades 6 to return to their open position.

STOPPING THE DOWN WARD ROTATION OF THE RESETTING CRANK The reversemovement of the above-mentioned parts continues until it is terminatedin response to a cam 57 moving into engagement with a limit switch 58 toeffect its operation. The cam 57 is shown in FIG. 9 to be attached toone side of the resetting crank 22 at a point near the previouslydescribed cam 51. The limit switch 58 is mounted on a bracket 60 that isattached to the frame 35 of the valve-closing equipment.

FIG. 9 shows the cam 57 in engagement with the limit switch 58. However,the portion of the resetting crank 22, that is shown in solid lines inFIG. 9, represents the idle position of the resetting crank 22 as isillustrated in FIG. 4. It should be noted that, prior to the occurrenceof the reverse movement of the resetting crank 22, this portion of theresetting crank 22 had been rotated upward to its active position as isillustrated in FIG. 6. This active position of the resetting crank 22 isrepresented with broken lines in FIG. 9. The rotation of the resettingcrank 22 to its active position causes the cam 57 to be rotated upwardout of engagement with the limit switch 58. This permits the limitswitch 58 to become closed as is represented in FIG. 10.

When the resetting crank 22 is now rotated to return to its idleposition, the cam 57 is carried into engagement with the limit switch 58as is illustrated in FIG. 9. This action operates and opens the limitswitch 58 thereby opening the energizing circuit of the relay 50. Thiscauses the relay 50 to release its armature thus opening the reversepower supply circuit 56 of the motor 38. Accordingly, the reverserotational movements of the resetting crank 22 and the actuator crank 11are now terminated. The manually operable switch 55, which has beenmaintained closed during this movement of the resetting crank 22, cannow be moved to its open position that is shown in FIG. 10. It should benoted that the terminating function of the cam 57 is so designed thatthe above mentioned reverse movements are not terminated until thelouver blades 6 are fully restored to their normally open position.

LOCKING THE RESETTING CRANK It should be noted that, when the motor 38is not energized, the pinion gear 41 is held stationary due to the factthat it is coupled to the motor 38 by a conventional worm gear reductiondrive mechanism 70 that is represented in FIG. 9. The reduction gearmechanism 70, which is of a type well known to those skilled in the art,is so designed that it does not allow the pinion gear 41 to rotateunless the motor 38 is energized. Accordingly, since the pinion gear 41is normally locked in a stationary position by the reduction gearmechanism 70, the pinion gear 41 functions, in turn, through itsengagement with the gear teeth 42 on the rim of the resetting crank 22,to hold or lock the resetting crank 22 in a normally stationaryposition.

As a result, due to the above-mentioned pinning action between theactuator crank 1 l and the resetting crank 22, the actuator crank 11 isnormally prevented from rotating. Therefore, this locked, or stationary,condition of the actuator crank 11 imposes a restriction upon themovement of the operating rod 10 during the time that the rollers 17 arein their interposed position. This pinned and stationary condition ofthe actuator crank 11 renders the torque exerted by the torsion spring15 ineffective to rotate the actuator crank 11 at this time.

UNLOCKING THE LOCKING MEANS It was stated above, in describing theprocedure that should be followed in tilting the louver blades 6 totheir closed position, that the operating rod 10 cannot be moved to itsoperated position until the locking means, which comprise the rollers17, has released the actuator crank 11 for rotation thereof. It was alsoexplained above that the rollers 17 are normally held in their lockingposition by pressure exerted by the normally energized solenoid 29. Itwas further stated above that the blocking force presented by thesolenoid 29 can be overcome by several different methods. These methodswill now be described.

UNLOCKING BY MANUAL MEANS The simplest method is to open manually anormally closed circuit 59 which is adapted to energize the solenoid 29.This energizing circuit 59, which is illustrated in FIG. 11, serves toconnect a suitable source 61 of electric energy to the winding of thesolenoid 29. A manually operable switch 62, which is normally closed, isconnected in series with the energizing circuit 59 so that, by manuallyopening the switch 62, the energizing circuit 59 will be opened and thesolenoid 29 will become deenergized.

Accordingly, the plunger 28 of the solenoid 29 will now cease its normalopposition to the force exerted by the trigger spring 24 and the triggerplunger 20. Therefore, the trigger plunger 20 will now move toward theright in FIG. 7 thus pushing the rollers 17 into the cavity 31 in theresetting crank 22 and thereby releasing the actuator crank 11 forrotation in response to the driving force exerted by the torsion spring15. The louver blades 6 will now be moved to their closed position inthe manner described above. The solenoid 29 can be subsequentlyreenergized by manually closing the switch 62 either during or after theabove described upward rotation of the resetting crank 22.

UNLOCKING WITH A BLAST-SENSING DEVICE A second method is to employ asuitable conventional blastsensing device 63, such as a remotely locatedblast-pressure detector or a gamma detector, which, as is well known tothose skilled in the art, will produce an electric output in response tothe occurrence of a blast. The electric output from the blast-sensingdevice 63 is adapted to open an obvious circuit 65 which is normallyclosed for energizing a relay 64, as is shown in FIG. 11. The opening ofthe circuit 65 causes the normal energized relay 64 to becomedeenergized. Accordingly, the relay 64 will now release its normallyoperated armature thereby opening the energizing circuit 59 of thesolenoid 29. This deenergization of the solenoid 29 effects the releaseof the rollers 17 in the same manner as that described above and foraccomplishing the same results, i.e., rotation of the actuator crank 11and the consequent closure of the louver blades 6.

After the effects of the blast have subsided, the electric output fromthe blast-sensing device 63 is discontinued thereby effecting thereclosing of the energizing circuit 65 with the consequentreenergization of the relay 64. This subsequent reenergization of therelay 64 will cause it to operate its armature thereby reclosing theenergizing circuit 59 to effect the reenergization of the solenoid 29.This restores the system to the condition required for reopening thelouver blades 6.

UNLOCKING WITH AERODYNAMIC TORQUE A third method is to utilize theaerodynamic torque which is generated at the louver blades 6 and whichis applied by them to the operating rod 10 when a sudden over-pressureimpinges upon the valve-closure system. This is accomplished byemploying an aerodynamically operated trigger crank 66 which ispositioned adjacent to the actuator crank 11 and which is rotatablymounted on the same pivot rod 14 as is indicated in FIG. 3. The left endof this aerodynamic crank 66 extends to the operating rod 10 and has anarcuate slot 67 formed therein as is best seen in FIG. 16. A pin 68,which is attached to the operating rod 10, as is best shown in FIG. 3,protrudes through the slot 67. Thus, the pin 68 and the operating rod 10serve to couple the aerodynamic crank 66 to the plurality of louverblades 6.

When a blast occurs, its overpressure impinges on the louver blades 6and, because of their cross-sectional shape, applies a downward torqueto them and they, in turn, translate this into a downward force upon theoperating rod 10. The rod 10 accordingly moves downward carrying with itthe pin 68 and thereby forcing the associated end of the aerodynamiccrank 66 to rotate downward about the pivot rod 14. When the downwardtorque exerted by the louver blades 6 is sufficiently great, as isexplained hereafter, it will initiate the movement of the aerodynamiccrank 66 from its idle or unrotated position, shown in FIG. 4, to itsactive or rotated position. Thus, the overpressure of the blast effectsthe rotation of the aerodynamic crank 66 about the pivot rod 14.

It should be noted that, when the actuator crank 11 is released forrotation by either of the two methods previously described above, itpulls the operating rod 10 downward in the manner explained above. This,in turn, causes the pin 68 to move downward thereby forcing theaerodynamic crank 66 to rotate in the manner described immediatelyabove. However, since the actuator crank 11 is also rotating, theaccompanying rotation of the aerodynamic crank 66 performs no usefulfunction at this time. Whenever the actuator crank 11 has been rotatedto effect the closing of the louver blades 6, the arcuate slot 67 willhave been moved toward the left, as is shown in FIG. 5, so that at anypoint during subsequent reopening of the louver blades 6, theaerodynamic crank 66 can respond to a blast pressure wave and canreclose the louver blades 6 if they are partly opened.

THE BIASING MEANS FOR THE OPERATING ROD Since, in spite of the normallylocked condition of the actuator crank 11, the operating rod must movedownward to a certain extent in order to initiate rotation of theaerodynamic trigger crank 66, a limited degree of freedom of movement isprovided for the operating rod 10 by mounting the actuator coupling pin12 in two slots 69 formed in opposite sides of the hollow operating rod10. Due to the fact that, at this time, the actuator coupling pin 12 isheld stationary, the operating rod 10 can move up and down within thelimits imposed by the lengths of the slots 69.

Normally, the operating rod 10 is pushed upward, to the upper limitpermitted by the slots 69, by means of a coiled biasing spring 71. Thisbiasing spring 71 is under compression and is coiled around the blade 13which, as was previously described, is vertically disposed inside therod 10 with its shouldered end in engagement with the coupling pin 12,as is represented in FIG. 16.

The lower end of the biasing spring 71 abuts against the top edge of theshouldered portion of the blade 13, and the upper end of the spring 71pushes upward against the bottom of a small block 72 which is securelyfastened inside the cavity formed by the hollow interior of the rod 10.This block 72 has a central slot formed therein for receiving the upperend of the blade 13. Accordingly, when the rod 10 moves downward andfurther compresses the spring 71, the slot in the block 72 will slidedownward around the upper portion of the blade 13.

Normally, since the spring 71 is under compression, it pushes againstthe block 72 and thus forces the operating rod 10 upward to the furthestextent permitted by the slots 69. As a result, the bottoms of the slots69 normally abut against the coupling pin 12. Also, the position of thepin 68 is normally toward the left end of the arcuate slot 67 in theaerodynamic crank 66 as is shown in FIG. 16 and also in FIG. 4. It cantherefore be understood that the downward force exerted by the louverblades 6 upon the operating rod 10, as a result of the overpressure of ablast, will not be effective to move the rod 10 downward unless it isgreater than the opposing force exerted by the biasing spring 71.

When the overpressure of a blast causes the downward force exerted bythe louver blades 6to exceed the biasing force of the spring 71, theoperating rod 10 will be forced downward so that the top edges of theslots 69 will approach the top edge of the coupling pin 12. This actionfurther compresses the spring71 by forcing the block 72 downward overthe blade 13. The downward movement of the operating rod 10 forcestheadjacent, or left, end portion of the aerodynamic trigger crank 66 torotate downward correspondingly and thereby causes the other, or right,end portion of the aerodynamic crank 66 to rotate upward as wasexplained above.

As is indicated in FIG. 3, a small block 73 is adapted to be securelyfastened to the right end portion of the aerodynamic trigger crank 66.This block 73 functions as a clamp for holding a shaft on which atrigger roller 74 is rotatably mounted. As is represented in FIG. 8, thetrigger roller 74 protrudes beyond the right edge of the block 73. Thus,the trigger roller 74 is mounted to rotate in a plane which is tangentto the end of the actuator crank 66.

Another small block 77 is located near the first block 73. As isindicated by the broken lines in FIG. 3, this block 77 is adapted to befixedly fastened to the block 26 which is designed to be attached to theactuator crank 11. The block 77 is mounted in such a manner as tooverlap the right edge of the aerodynamic trigger crank 66 withoutnormally applying any binding force to it. The purpose of this block 77is to provide a stabilizing support for limiting the extent of anydeflection or motion of the aerodynamic crank 66 outside of its desiredplane of rotation.

A somewhat similar block 78 is fixedly secured to the resetting crank 22near the toothed edge thereof as is best seen in FIG. 8. A portion ofthe block 78 overlaps the right edge of the actuator crank 11 but doesnot normally apply any binding force to it. This block 78 functions torestrict the motion of the actuator crank 1 l to its desired plane bystabilizing, or limiting, the extent of any deflection therefrom whichmight tend to be caused by axial forces produced by the tripping of thelocking rollers 17.

THE AERODYNAMIC TRIGGER MEANS As is shown in FIG. 7 and also in FIG. 8,the block 26, which is attached to the actuator crank 11, has one end ofan instrumentality, constituted by a spring-hinged lever-cam 75, fixedlysecured thereto in the manner indicated in FIG. 3. The unattached end ofthis lever-cam 75 is tilted outward in a direction leading toward theaerodynamic trigger crank 66 for forming a ramp 76 as is best seen inFIG. 7. This instrumentality, or lever-cam, 75 is designed to bearagainst the roller 74 with a frictional engagement. As is best shown inFIG. 7, the trigger roller 74 normally engages that portion of thelever-cam 75 which is opposite that end of the trigger plunger 20 whichis normally protruding through a hole in the block 26. The lever cam 75is positioned close to the protruding end of the trigger plunger 20 andmay touch it lightly. It should be noted that, when the trigger roller74 is in the position shown in FIG. 7, neither it nor the lever-cam 75apply any significant pressure to the protruding end of the triggerplunger 20.

When the right end portion of the aerodynamic trigger crank 66 isrotated upward, as was described above, it carries with it the triggerroller 74. In thus moving upward, the frictional engagement between thelever-cam 75 and the roller 74 produces rotation of the roller 74. Theupward movement also causes the trigger roller 74 to move against theoutwardly extending ramp 76 of the lever-cam 75.

Since the lever-cam 75 is spring-hinged, the movement, or rotation, ofthe trigger roller 74 upward along the ramp 76 will force the lever-cam75 to move toward the face of the block 26 on the actuator crank 11. Atthe same time, the intermediate portion of the lever-cam 75 will beforced to move toward the block 26 and will consequently press againstthe protruding end of the trigger plunger 20. This pressure istransmitted to the enlarged head of the trigger plunger 20 which, inturn, applies pressure to the left side of the locking rollers 17.

When this pressure applied to the left side of the rollers 17, combinedwith the pressure exerted by spring 24, is greater than the opposingpressure applied to the other side of the rollers 17 by the operateddisk 27 and plunger 28 of the solenoid 29, the disk 27 and the plunger28 will be forced toward the right in FIG. 7. Accordingly, the lockingrollers 17 will now be pushed into the cavity 31 which is formed in oneside of the resetting crank 22. This action unlocks the actuator crank11 and allows it to be rotated by the driving force exerted by thetorsion spring 15 in the manner described above and thereby effects thetilting of the louver blades 6 and the closing of the opening in theduct 1. Thus, the trigger roller 74 constitutes rotatable initiatingmeans which, through its rotation, effects the rotation of the actuatingmeans formed by the actuator crank 11. Also, the aerodynamic crank 66constitutes rotatable control means which, through its rotation, effectsthe rotation of the initiating means constituted by the trigger roller74.

What is claimed is:

l. A blast-actuated valve-closure system adapted for closing an openingin response to the overpressure of a blast,

said system comprising movable covering means having a closed positionfor covering said opening and an open position for uncovering saidopening,

said covering means having a surface adapted for receiving the force ofa blast pressure wave,

rotatable actuating means adapted for effecting through its rotation themovement of said covering means from said open position to said closedposition,

rotatable initiating means adapted for effecting by its rotation theinitiation of the rotation of said actuating means,

and rotatable control means adapted for effecting through its rotationthe rotation of said initiating means,

said control means being further adapted to be rotated in response tothe impingement of a blast pressure wave on said covering means.

2. A blast-actuated valve-closure system in accordance with claim 1 andfurther comprising locking means having a first position adapted forblocking rotation of said actuating means,

said locking means having a second position adapted for unblockingrotation of said actuating means,

said rotatable initiating means including a roller adapted for effectingthrough its rotation the placing of said locking means in its secondposition and for thereby effecting the initiation of the rotation ofsaid actuating means,

and said rotatable control means having means adapted for carrying saidinitiating means during rotation of said control means and for therebyeffecting rotation of said roller.

3. A blast-actuated valve-closure system in accordance with claim 2 andfurther comprising an instrumentality attached to said actuating meansand adapted to bear against said roller with a frictional engagementadapted for producing rotation of said roller in response to thecarrying of said roller by said control means during its rotation.

4. A blast-actuated valve-closure system in accordance with claim 3wherein said instrumentality is constituted by a springhinged lever-camhaving a tilted portion for forming a ramp,

said ramp being adapted for sloping in a direction away from saidlocking means.

5. A blast-actuated valve-closure system in accordance with claim 1wherein said covering means comprise a plurality of parallelly disposedlouver blades,

and further comprising coupling means for coupling said plurality oflouver blades to a portion of said control means,

said coupling means including an operating rod,

a plurality of connecting means each having one end attached to themiddle of a respectively different one of said louver blades and havinganother end attached to said operating rod,

said control means having means defining an arcuate slot formed in saidportion thereof,

and a pin attached to said operating rod and disposed in said slot,

the position of said pin in said slot being adapted to be changed inresponse to rotation of said control means.

6. A blast-actuated valve-closure system in accordance with claim 5wherein said operating rod includes means defining a cavity formedtherein,

and further comprising an instrumentality extending through said rod andinto said cavity,

a block fixedly fastened inside said cavity,

biasing means for normally forcing said pin to move toward one endofsaid slot,

said biasing means including a blade having a shouldered end,

said blade being slidably disposed within said cavity with saidshouldered end in engagement with said instrumentality,

and spring means encircling said blade for pressing in one directionagainst said shouldered end of said blade and for pressing in anopposite direction against said block.

7. A blast-actuated valve-closure system in accordance with claim 1 andfurther comprising a shaft,

and means for mounting both said actuating means and said control meanson said shaft for rotation thereabout.

8. A blast-actuated valve-closure system in accordance with claim 1wherein said actuating means has an unrotated position in which itnormally rests and a rotated position to which it moves in response toits rotation,

and further comprising rotatable resetting means adapted for returningsaid actuating means from its rotated position to its unrotatedposition.

9. A blast-actuated valve-closure system in accordance with claim 8 andfurther comprising a shaft,

and means for mounting said actuating means and said control means andsaid resetting means on said shaft for rotation thereabout.

10. A blast-actuated valve-closure system adapted for closing an openingin response to the overpressure of a blast,

said system comprising movable covering means having a closed positionfor covering said opening and an open position for uncovering saidopening,

said covering means having a surface adapted for receiving the force ofa blast pressure wave,

rotatable actuating means adapted for effecting through its rotation themovement of said covering means from said open position to said closedposition,

and rotatable control means adapted for effecting through its rotationthe consequent rotation of said actuating means,

said control means being further adapted to be rotated in response tothe impingement of a blast pressure wave on said covering means.

11. A blast-actuated valve-closure system in accordance with claim 1 andfurther comprising rotatable initiating means adapted for effectingthrough its rotation the initiation of the rotation of said actuatingmeans,

said initiating means having its rotation effected in response to therotation of said control means.

12. A blast-actuated valve-closure system adapted for closing an openingin response to the overpressure of a blast,

said system comprising movable covering means having a closed positionfor covering said opening and an open position for uncovering saidopening,

said covering means having a surface adapted for receiving the force ofa blast pressure wave,

rotatable actuating means adapted for effecting through its rotation themovement of said covering means from said open position to said closedposition,

control means for effecting the initiation of the rotation of saidactuating means from an idle position to an active position,

and resetting means for returning said actuating means from said activeposition to said idle position.

13. A blast-actuated valve-closure system in accordance with claim 12and further comprising locking means having a first position adapted forholding said actuating means in its idle position,

said locking means having a second position adapted for releasing saidactuating means from its idle position for movement to its operatedposition,

said locking means including a composite detent having two holdingmeans,

one of said holding means being fixedly attached to said resettingmeans, I

and the other of said holding means being secured to said actuatingmeans.

14. A blast-actuated valve-closure system in accordance with claim 13wherein one of said holding means includes a holding finger and theother of said holding means includes a double finger having two fingerelements spaced apart by a distance at least equal to the width of saidholding finger.

15. A blast-actuated valve-closure system in accordance with claim 14wherein said holding means that is fixedly attached to said resettingmeans is constituted by said holding finger,

said holding finger having an end portion,

and further comprising means defining an arcuate groove in saidactuating means for receiving therein said end portion of said holdingfinger.

16 A valve-closure system in accordance with claim 12 wherein saidactuating means include means defining a cavity therein and wherein saidresetting means include means defining a cavity therein,

and further comprising locking means adapted for locking said actuatingmeans in its idle position,

said locking means including a first portion and a second portion,

said first portion being fixedly disposed in said cavity in saidactuating means, i

and said second portion being fixedly disposed in said cavity in saidresetting means.

17. A valve-closure system in accordance with claim 16 wherein one ofsaid portions of said locking means includes a single holding pin,

and wherein the other of said portions of said locking means includes adouble holding pin having two pin elements spaced apart by a distance atleast equal to the diameter of said single holding pin.

18. A valve-closure system in accordance with claim 16 and furthercomprising roller means normally having a position interposed betweensaid first and second portions of said locking means,

and first pushing means positioned in a first one of said cavities andadapted for pushing said roller means into a second one of said cavitiesfor effecting the unlocking of said actuating means.

19. A valve-closure system in accordance with claim 18 and furthercomprising second pushing means positioned in said second one of saidcavities and adapted for pushing said roller means out of said secondone of said cavities after having been pushed therein by said firstpushing means.

20. A valve-closure system in accordance with claim 19 and furthercomprising activating means for effecting movement of said secondpushing means,

said activating means including spring means,

and a cam-operable instrumentality adapted for compressing saidspring'means for effecting movement of said second pushing means. 21. Avalve-closure system in accordance with claim 16 and further comprisingroller means normally having a position interposed between said firstand second portions of said locking means,

first pushing means positioned in a first one of said cavities andadapted for exerting pushing force against said roller means in adirection toward the second one of said cavities, 1

second pushing means positioned in said second one of said cavities andadapted for exerting pushing force against said roller means in adirection toward said first one of said cavities.

22. A valve-closure system in accordance with claim 21 and furthercomprising trigger means for effecting the movement of said roller meansout of said interposed position,

said trigger means including means for causing the pushing force exertedby one of said pushing means to become relatively stronger than thepushing force of the other of said pushing means.

23. A system for alternatively covering and uncovering an opening,

said system comprising covering means having a closed position forcovering said opening and an open position for uncovering said opening,

operating means adapted for moving said covering means alternativelyfrom one of said positions to the other of said positions,

said operating means having an unoperated position for holding saidcovering means in its open position and an operated position for holdingsaid covering means in its closed position,

actuating means adapted for moving said operating means from itsunoperated position to its operated position,

said actuating means having an idle position for holding said operatingmeans in its unoperated position and an active position for holding saidoperating means in its operated position,

locking means having a first position adapted for holding said actuatingmeans in its idle position,

said locking means having a second position adapted for releasing saidactuating means from its idle position,

trigger means adapted for moving said locking means from its firstposition to its second position for effecting the release of saidactuating means from its idle position,

rotatable driving means responsive to said release of said actuatingmeans for driving said actuating means to its active position wherebysaid operating means is moved to its operated position thereby movingsaid covering means to its closed position,

and resetting means adapted for returning said actuating means from itsactive position to its idle position.

24. A system in accordance with claim 23 wherein said rotatable drivingmeans includes torsion means,

and further comprising coupling means for coupling said torsion means tosaid actuating means,

said torsion means being normally in a wound condition and in a state oftorsional stress,

and said torsion means being adapted to assume an at least partlyunwound condition in response to driving said actuating means to itsactive position.

25. A system in accordance with claim 24 wherein said resetting meanshas an unoperated position and alternatively has an operated position,

said resetting means being normally in its unoperated position when saidactuating means is in its idle position,

and gear means adapted for producing a driving action for placing saidresetting means in its operated position in response to the movement ofsaid actuating means to its active position.

26. A system in accordance with claim 25 and further comprising controlmeans for reversing the driving action of said gear means for effectingthe return of said resetting means from its operated position to itsunoperated position,

said actuating means being adapted to be returned from its activeposition to its idle position in response to the movement of saidresetting means from its operated position to its unoperated position,

and said torsion spring being adapted to resume its wound condition andreturn to its state of being torsionally stressed in response to themovement of said resetting means from its operated position to itsunoperated position.

27. A system for alternatively covering and uncovering an opening,

said system comprising covering means including a plurality ofparallelly disposed louver blades having a closed position for coveringsaid opening and an open position for uncovering said opening,

- an operating rod having means for connecting it individually to eachof said louver blades for alternatively moving them from one of saidpositions to the other of said positions,

said operating rod having an unoperated position for holding said louverblades in their open position and an operated position for holding themin their closed position,

a rotatable actuating crank adapted for moving said operating rod fromone of its positions to the other of its positions,

said crank having two end portions,

a pivot rod for rotatably supporting said actuating crank at a pointintermediate said end portions,

said actuating crank having an idle position for holding said operatingrod in its unoperated position and an active position for holding saidoperating rod in its operated position,

and connecting means for connecting one end portion of said rotatableactuating crank to said operating rod for effecting movement thereof.

28. A system in accordance with claim 27 and further comprising torsiondriving means adapted for imparting rotary motion to one of said endportions of said actuating crank for ef fecting rotation of saidactuating crank from its idle position to its active position,

said connecting means being responsive to said rotation of saidactuating crank for efiecting movement of said operating rod from itsunoperated position to its operated position and for thereby moving saidlouver blades from their open position to their closed position,

and a rotatable resetting crank rotatably mounted on said pivot rod in aposition adjacent to one side of said actuator crank,

said resetting crank being adapted for effecting the return movement ofsaid actuating crank from its active position to its idle position andfor thereby effecting the return of said operating rod to its unoperatedposition and the consequent return of said louver blades to their openposition.

29. A system in accordance with claim 28 and further comprising gearmeans adapted for normally holding said resetting crank in a stationarycondition,

and locking means adapted for normally holding said actuator crank in astationary condition thereby overcoming the driving influence of saidtorsion driving means,

said locking means including means for normally pinning said actuatorcrank to said resetting crank.

30. A system in accordance with claim 29 and further comprising triggermeans for effecting the unpinning of said actuator crank from saidresetting crank,

said torsion driving means being responsive to said unpinning of saidactuator crank for effecting the rotation of said actuator crank to itsactive position and for thereby effecting the movement of said operatingrod to its operated position with the consequent movement of said louverblades to their closed position.

31. A system in accordance with claim 30 and further comprisingoperating means adapted for operating said gear means for rotating saidresetting crank in the same direction as that in which said actuatorcrank was rotated,

and means for limiting the extent of said rotation of said resettingcrank to the same extent as that in which said actuator crank wasrotated from its idle position to its active position,

and said locking means including means adapted for repinning saidactuator crank while in its active position to said rotated resettingcrank.

32. A system in accordance with claim 31 and further comprisingreversing means adapted for reversing the operation of said gear meansfor effecting the rotation of said resetting crank in a directionopposite to that of its previous rotation,

and means for limiting the extent of said reverse rotation of saidresetting crank to the same extent as that of its previous rotation,

said reverse rotation of said resetting crank being adapted to effectthe return of said repinned actuator crank to its idle position.

1. A blast-actuated valve-closure system adapted for closing an openingin response to the overpressure of a blast, said system comprisingmovable covering means having a closed position for covering saidopening and an open position for uncovering said opening, said coveringmeans having a surface adapted for receiving the force of a blastpressure wave, rotatable actuating means adapted for effecting throughits rotation the movement of said covering means from said open positionto said closed position, rotatable initiating means adapted foreffecting by its rotation the initiation of the rotation of saidactuating means, and rotatable control means adapted for effectingthrough its rotation the rotation of said initiating means, said controlmeans being further adapted to be rotated in response to the impingementof a blast pressure wave on said covering means.
 2. A blast-actuatedvalve-closure system in accordance with claim 1 and further comprisinglocking means having a first position adapted for blocking rotation ofsaid actuating means, said locking means having a second positionadapted for unblocking rotation of said actuating means, said rotatableinitiating means including a roller adapted for effecting through itsrotation the placing of said locking means in its second position andfor thereby effecting the initiation of the rotation of said actuatingmeans, and said rotatable control means having means adapted forcarrying said initiating means during rotation of said control means andfor thereby effecting rotation of said roller.
 3. A blast-actuatedvalve-closure system in accordance with claim 2 and further comprisingan instrumentality attached to said actuating means and adapted to bearagainst said roller with a frictional engagement adapted for producingrotation of said roller in response to the carrying of said roller bysaid control means during its rotation.
 4. A blast-actuatedvalve-closure system in accordance with claim 3 wherein saidinstrumentality is constituted by a spring-hinged lever-cam having atilted portion for forming a ramp, said ramp being adapted for slopingin a direction away from said locking means.
 5. A blast-actuatedvalve-closure system in accordance with claim 1 wherein said coveringmeans comprise a plurality of parallelly disposed louver blades, andfurther comprising coupling means for coupling said plurality of louverblades to a portion of said control means, said coupling means includingan operating rod, a plurality of connecting means each having one endattached to the middle of a respective1y different one of said louverblades and having another end attached to said operating rod, saidcontrol means having means defining an arcuate slot formed in saidportion thereof, and a pin attached to said operating rod and disposedin said slot, the position of said pin in said slot being adapted to bechanged in response to rotation of said control means.
 6. Ablast-actuated valve-closure system in accordance with claim 5 whereinsaid operating rod includes means defining a cavity formed therein, andfurther comprising an instrumentality extending through said rod andinto said cavity, a block fixedly fastened inside said cavity, biasingmeans for normally forcing said pin to move toward one end of said slot,said biasing means including a blade having a shouldered end, said bladebeing slidably disposed within said cavity with said shouldered end inengagement with said instrumentality, and spring means encircling saidblade for pressing in one direction against said shouldered end of saidblade and for pressing in an opposite direction against said block.
 7. Ablast-actuated valve-closure system in accordance with claim 1 andfurther comprising a shaft, and means for mounting both said actuatingmeans and said control means on said shaft for rotation thereabout.
 8. Ablast-actuated valve-closure system in accordance with claim 1 whereinsaid actuating means has an unrotated position in which it normallyrests and a rotated position to which it moves in response to itsrotation, and further comprising rotatable resetting means adapted forreturning said actuating means from its rotated position to itsunrotated position.
 9. A blast-actuated valve-closure system inaccordance with claim 8 and further comprising a shaft, and means formounting said actuating means and said control means and said resettingmeans on said shaft for rotation thereabout.
 10. A blast-actuatedvalve-closure system adapted for closing an opening in response to theoverpressure of a blast, said system comprising movable covering meanshaving a closed position for covering said opening and an open positionfor uncovering said opening, said covering means having a surfaceadapted for receiving the force of a blast pressure wave, rotatableactuating means adapted for effecting through its rotation the movementof said covering means from said open position to said closed position,and rotatable control means adapted for effecting through its rotationthe consequent rotation of said actuating means, said control meansbeing further adapted to be rotated in response to the impingement of ablast pressure wave on said covering means.
 11. A blast-actuatedvalve-closure system in accordance with claim 1 and further comprisingrotatable initiating means adapted for effecting through its rotationthe initiation of the rotation of said actuating means, said initiatingmeans having its rotation effected in response to the rotation of saidcontrol means.
 12. A blast-actuated valve-closure system adapted forclosing an opening in response to the overpressure of a blast, saidsystem comprising movable covering means having a closed position forcovering said opening and an open position for uncovering said opening,said covering means having a surface adapted for receiving the force ofa blast pressure wave, rotatable actuating means adapted for effectingthrough its rotation the movement of said covering means from said openposition to said closed position, control means for effecting theinitiation of the rotation of said actuating means from an idle positionto an active position, and resetting means for returning said actuatingmeans from said active position to said idle position.
 13. Ablast-actuated valve-closure system in accordance with claim 12 andfurther comprising locking means having a first position adapted forholding said actuating means in its idle position, said locking meanshaving a second position adapted for releasing said actuating means fromits idle position for movement to its operated position, said lockingmeans including a composite detent having two holding means, one of saidholding means being fixedly attached to said resetting means, and theother of said holding means being secured to said actuating means.
 14. Ablast-actuated valve-closure system in accordance with claim 13 whereinone of said hoLding means includes a holding finger and the other ofsaid holding means includes a double finger having two finger elementsspaced apart by a distance at least equal to the width of said holdingfinger.
 15. A blast-actuated valve-closure system in accordance withclaim 14 wherein said holding means that is fixedly attached to saidresetting means is constituted by said holding finger, said holdingfinger having an end portion, and further comprising means defining anarcuate groove in said actuating means for receiving therein said endportion of said holding finger.
 16. A valve-closure system in accordancewith claim 12 wherein said actuating means include means defining acavity therein and wherein said resetting means include means defining acavity therein, and further comprising locking means adapted for lockingsaid actuating means in its idle position, said locking means includinga first portion and a second portion, said first portion being fixedlydisposed in said cavity in said actuating means, and said second portionbeing fixedly disposed in said cavity in said resetting means.
 17. Avalve-closure system in accordance with claim 16 wherein one of saidportions of said locking means includes a single holding pin, andwherein the other of said portions of said locking means includes adouble holding pin having two pin elements spaced apart by a distance atleast equal to the diameter of said single holding pin.
 18. Avalve-closure system in accordance with claim 16 and further comprisingroller means normally having a position interposed between said firstand second portions of said locking means, and first pushing meanspositioned in a first one of said cavities and adapted for pushing saidroller means into a second one of said cavities for effecting theunlocking of said actuating means.
 19. A valve-closure system inaccordance with claim 18 and further comprising second pushing meanspositioned in said second one of said cavities and adapted for pushingsaid roller means out of said second one of said cavities after havingbeen pushed therein by said first pushing means.
 20. A valve-closuresystem in accordance with claim 19 and further comprising activatingmeans for effecting movement of said second pushing means, saidactivating means including spring means, and a cam-operableinstrumentality adapted for compressing said spring means for effectingmovement of said second pushing means.
 21. A valve-closure system inaccordance with claim 16 and further comprising roller means normallyhaving a position interposed between said first and second portions ofsaid locking means, first pushing means positioned in a first one ofsaid cavities and adapted for exerting pushing force against said rollermeans in a direction toward the second one of said cavities, secondpushing means positioned in said second one of said cavities and adaptedfor exerting pushing force against said roller means in a directiontoward said first one of said cavities.
 22. A valve-closure system inaccordance with claim 21 and further comprising trigger means foreffecting the movement of said roller means out of said interposedposition, said trigger means including means for causing the pushingforce exerted by one of said pushing means to become relatively strongerthan the pushing force of the other of said pushing means.
 23. A systemfor alternatively covering and uncovering an opening, said systemcomprising covering means having a closed position for covering saidopening and an open position for uncovering said opening, operatingmeans adapted for moving said covering means alternatively from one ofsaid positions to the other of said positions, said operating meanshaving an unoperated position for holding said covering means in itsopen position and an operated position for holding said covering meansin its closed position, actuating means adapted for moving saidoPerating means from its unoperated position to its operated position,said actuating means having an idle position for holding said operatingmeans in its unoperated position and an active position for holding saidoperating means in its operated position, locking means having a firstposition adapted for holding said actuating means in its idle position,said locking means having a second position adapted for releasing saidactuating means from its idle position, trigger means adapted for movingsaid locking means from its first position to its second position foreffecting the release of said actuating means from its idle position,rotatable driving means responsive to said release of said actuatingmeans for driving said actuating means to its active position wherebysaid operating means is moved to its operated position thereby movingsaid covering means to its closed position, and resetting means adaptedfor returning said actuating means from its active position to its idleposition.
 24. A system in accordance with claim 23 wherein saidrotatable driving means includes torsion means, and further comprisingcoupling means for coupling said torsion means to said actuating means,said torsion means being normally in a wound condition and in a state oftorsional stress, and said torsion means being adapted to assume an atleast partly unwound condition in response to driving said actuatingmeans to its active position.
 25. A system in accordance with claim 24wherein said resetting means has an unoperated position andalternatively has an operated position, said resetting means beingnormally in its unoperated position when said actuating means is in itsidle position, and gear means adapted for producing a driving action forplacing said resetting means in its operated position in response to themovement of said actuating means to its active position.
 26. A system inaccordance with claim 25 and further comprising control means forreversing the driving action of said gear means for effecting the returnof said resetting means from its operated position to its unoperatedposition, said actuating means being adapted to be returned from itsactive position to its idle position in response to the movement of saidresetting means from its operated position to its unoperated position,and said torsion spring being adapted to resume its wound condition andreturn to its state of being torsionally stressed in response to themovement of said resetting means from its operated position to itsunoperated position.
 27. A system for alternatively covering anduncovering an opening, said system comprising covering means including aplurality of parallelly disposed louver blades having a closed positionfor covering said opening and an open position for uncovering saidopening, an operating rod having means for connecting it individually toeach of said louver blades for alternatively moving them from one ofsaid positions to the other of said positions, said operating rod havingan unoperated position for holding said louver blades in their openposition and an operated position for holding them in their closedposition, a rotatable actuating crank adapted for moving said operatingrod from one of its positions to the other of its positions, said crankhaving two end portions, a pivot rod for rotatably supporting saidactuating crank at a point intermediate said end portions, saidactuating crank having an idle position for holding said operating rodin its unoperated position and an active position for holding saidoperating rod in its operated position, and connecting means forconnecting one end portion of said rotatable actuating crank to saidoperating rod for effecting movement thereof.
 28. A system in accordancewith claim 27 and further comprising torsion driving means adapted forimparting rotary motion to one of said end portions of said actuatingcrank for effecTing rotation of said actuating crank from its idleposition to its active position, said connecting means being responsiveto said rotation of said actuating crank for effecting movement of saidoperating rod from its unoperated position to its operated position andfor thereby moving said louver blades from their open position to theirclosed position, and a rotatable resetting crank rotatably mounted onsaid pivot rod in a position adjacent to one side of said actuatorcrank, said resetting crank being adapted for effecting the returnmovement of said actuating crank from its active position to its idleposition and for thereby effecting the return of said operating rod toits unoperated position and the consequent return of said louver bladesto their open position.
 29. A system in accordance with claim 28 andfurther comprising gear means adapted for normally holding saidresetting crank in a stationary condition, and locking means adapted fornormally holding said actuator crank in a stationary condition therebyovercoming the driving influence of said torsion driving means, saidlocking means including means for normally pinning said actuator crankto said resetting crank.
 30. A system in accordance with claim 29 andfurther comprising trigger means for effecting the unpinning of saidactuator crank from said resetting crank, said torsion driving meansbeing responsive to said unpinning of said actuator crank for effectingthe rotation of said actuator crank to its active position and forthereby effecting the movement of said operating rod to its operatedposition with the consequent movement of said louver blades to theirclosed position.
 31. A system in accordance with claim 30 and furthercomprising operating means adapted for operating said gear means forrotating said resetting crank in the same direction as that in whichsaid actuator crank was rotated, and means for limiting the extent ofsaid rotation of said resetting crank to the same extent as that inwhich said actuator crank was rotated from its idle position to itsactive position, and said locking means including means adapted forrepinning said actuator crank while in its active position to saidrotated resetting crank.
 32. A system in accordance with claim 31 andfurther comprising reversing means adapted for reversing the operationof said gear means for effecting the rotation of said resetting crank ina direction opposite to that of its previous rotation, and means forlimiting the extent of said reverse rotation of said resetting crank tothe same extent as that of its previous rotation, said reverse rotationof said resetting crank being adapted to effect the return of saidrepinned actuator crank to its idle position.